1. Field of the Invention
This invention relates generally to an exhaust plenum chamber and more particularly to an exhaust plenum chamber for an internal combustion engine supercharged by a gas-dynamic pressure-wave machine.
2. Discussion of Background
The purpose of such an exhaust plenum chamber, on the one hand, is to collect the exhaust mass flows which is given off by the individual cylinders of an engine. On the other hand, the exhaust chamber reduces the pulsations caused by an engine. The reduction action is of particular importance when an engine is supercharged with a gas-dynamic pressure-wave machine. Overly strong exhaust pulsations can considerably affect the supercharging process in the pressure-wave machine, because they cause fluctuations of the wave propagation time. For the mode of operation of a pressure-wave machine, reference is made to CH-PS No. 378 595 or to the printed publication CH-T No. 123 143 of the applicant.
Now, however, the choice of the volume of an exhaust receiver represents a compromise in each case. On the one hand, a large volume is advantageous, because the reduction of pulsations becomes greater with increasing volume. But on the other hand, a large volume results in a delayed response of the supercharger to load and speed variations, because the time for scavenging the exhaust plenum chamber increases with increasing volume. Such a compromise is particularly difficult in the case of slightly supercharged engines with a small number of cylinders. In engines with a small number of cylinders, the smoothing action on the exhaust pulsations by the collection of the partial mass flows given off by the individual cylinders is poor or even nonexistent. Moreover, the pulsation frequency is low and makes a correspondingly large receiver volume necessary for an effective reduction. There is also the fact that the efficiency of the exhaust plenum chamber becomes poorer with decreasing supercharging. An almost insoluble problem is faced, for example, in arriving at this compromise in the case of a slightly supercharged two-cylinder diesel engine.